The present invention relates to pulse oximeter sensors, and in particular to techniques for shielding against ambient light and preventing delamination of flexible, disposable sensors.
A type of pulse oximeter sensor that is commonly used is a flexible, disposable sensor. It typically has multiple layers, with white layers on the outside visible to the user. The white gives the image of cleanliness and sterility, and also is opaque to certain wavelengths of light over the range of the photodetector""s sensitivity. An example of a sensor referring to a white opaque layer is set forth in U.S. Pat. No. 4,865,038.
A number of these sensors include metalized layers which can be either a conductive shield or a shield from ambient light. See, for example, U.S. Pat. Nos. 4,928,691; 5,246,003; 5,094,240; 5,054,488; and 4,964,408. U.S. Pat. No. 4,928,691 refers to the use of a red layer to avoid ambient light.
Ambient light can interfere with the operation of a pulse oximeter, especially under the bright lights of surgery or in outdoor, daylight conditions. While the use of a metal layer has been effective to shield from such ambient light, there is also a competing desire to have transparency in order to observe how a sensor is attached. In addition, the introduction of additional layers into the sensor is susceptible to sensor failure by delamination.
Accordingly, it would be desirable to have a sensor which would shield against ambient light, be resistant to delamination and have some transparency.
The present invention provides a pulse oximeter sensor having an opaque, metalized layer to shield from ambient light. The metalized layer surrounds the area of the light detector. In one embodiment, the sensor has a transparent portion, with the opaque, metalized layer covering only the portions around the light detector and other areas, such as a strip extending between the light detector and the emitter. In a preferred embodiment, the opaque, metalized layer is a strip which has a widened portion in the area around the light detector.
The widened portion of the metalized layer, in conjunction with widened portions that match on adjacent layers, resists delamination stresses.
In another aspect of the invention, the wires connecting to the emitter take an angular path, preferably crossing over from one side of the detector, across a center line between the emitter and detector, to an opposite side of the emitter. This angular path, as opposed to a straight path, disperses stresses caused by the wires, further inhibiting delamination or separation of the layers of the sensor.
In a preferred embodiment, the widened area of the metalized and adjacent layers has a semi-circular profile around the photodetector.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the accompanying drawing.